Nano NiO/AlMCM-41, a green synergistic, highly efficient and recyclable catalyst for the reduction of nitrophenols

Highly ordered mesoporous molecular sieves AlMCM-41 and a new NiO/AlMCM-41 nanocomposite were synthesized using a sol-gel method. Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and N-2 adsorption desorption analyses were used to examine the structure, morphology, size and phase composition of the synthesized NiO/AlMCM-41 nanocomposites. AlMCM-41 embedded with NiO nanoparticles was subsequently prepared using different nickel loadings in a direct synthetic route. The results show the successful deposition of NiO nanoparticles onto the framework of AlMCM-41. AlMCM-41 provides enormous benefits such as environmentally safe, economic viability and porosity when used as support for NiO nanoparticles. The excellent catalytic activities of AlMCM-41 and NiO/AlMCM-41 were investigated for the reduction of nitrophenols (4-NP, 2-NP) to aminophenols (4-AP, 2-AP) in water at ambient temperature. The best observed performance of reduction of NP with 100% conversion into analogous amino derivatives occurred within 6 min with an estimated rate constant of 0.46 min(-1). The efficiency of reduction was observed to increase as a function of NiO enrichment. The NiO/AlMCM-41 nanocomposite could be recycled and reused up to five times without noticeable change in its structure and activity. These properties make NiO/AlMCM-41 nanocomposite an ideal platform to study various heterogeneous catalytic processes which can have application in purification, catalysis, sensing devices, and green chemistry.